An internal combustion engine includes an engine body and engine components, such as a fuel injector, spark plug, and pressure sensor mounted on the engine body. The engine body also includes one or more engine coolant passages containing engine coolant in close proximity to the engine components. For example, engines often require a separate injector sleeve insert to separate coolant from the fuel injector. Many designs for injector sleeve insertion exist with varying degrees of robustness against coolant, fuel, and combustion gas, leaks, particularly at the end closest to the combustion event, i.e. the combustion chamber. The high local temperatures make elastomeric sealing a challenge. Also, high mechanical and thermal load cycling may create high stress at the sleeve/head seal interface. An internal combustion engine with a fuel injector may require a combustion seal to keep combustion gases in a combustion chamber of the engine from flowing into a passage surrounding the fuel injector. One challenge with such seals is that they may be inefficient at transporting or transferring heat away from a nozzle housing of the fuel injector, or if such seals transport heat away from a distal end of a nozzle element housing, the seals may have insufficient strength to resist yielding, which may ultimately permit leaks.